Impact of meltwater flow intensity on the spatiotemporal heterogeneity of microbial mats in the McMurdo Dry Valleys, Antarctica

The meltwater streams of the McMurdo Dry Valleys are hot spots of biological diversity in the climate-sensitive polar desert landscape. Microbial mats, largely comprised of cyanobacteria, dominate the streams which flow for a brief window of time (~10 weeks) over the austral summer. These communities, critical to nutrient and carbon cycling, display previously uncharacterized patterns of rapid destabilization and recovery upon exposure to variable and physiologically detrimental conditions. Here, we characterize changes in biodiversity, transcriptional responses and activity of microbial mats in response to hydrological disturbance over spatiotemporal gradients. While diverse metabolic strategies persist between marginal mats and main channel mats, data collected from 4 time points during the austral summer revealed a homogenization of the mat communities during the mid-season peak meltwater flow, directly influencing the biogeochemical roles of this stream ecosystem. Gene expression pattern analyses identified strong functional sensitivities of nitrogen-fixing marginal mats to changes in hydrological activities. Stress response markers detailed the environmental challenges of each microhabitat and the molecular mechanisms underpinning survival in a polar desert ecosystem at the forefront of climate change. At mid and end points in the flow cycle, mobile genetic elements were upregulated across all mat types indicating high degrees of genome evolvability and transcriptional synchronies. Additionally, we identified novel antifreeze activity in the stream microbial mats indicating the presence of ice-binding proteins (IBPs). Cumulatively, these data provide a new view of active intra-stream diversity, biotic interactions and alterations in ecosystem function over a high-flow hydrological regime.

Abstract OT2-05-03: Does minocycline mitigate chemotherapy induced neuroinflammation? A phase II randomized placebo controlled study

Background: Many breast cancer (BC) patients, particularly those who receive chemotherapy (chemo), experience affective symptoms and cognitive changes that can negatively impact their quality of life. Causal links between inflammatory mediators and the development of depressive-like behavior and cognitive defects, have been established in mouse models, including studies by our group showing increased microglial activation following chemo (A.C DeVries et al). Microglia are resident immune cells of the brain, which release proinflammatory cytokines when activated. Doxorubicin (DOX) induces microglial activation in the brain. Minocycline, a second generation tetracycline, has been shown to suppress inflammation by inhibiting microglial activation in CNS disease models. We hypothesize that (1) chemo activates microglia in the brains of women being treated for BC, which can precipitate or exacerbate depression, anxiety and cognitive deficits and (2) Minocycline administration during neoadjuvant or adjuvant chemo will prevent chemo-induced microglial activation and will reduce affective and cognitive symptom burden. Trial Design: This is a single center, Phase II, double blinded randomized study of minocycline (100 mg twice a day) vs placebo twice a day in women with BC receiving DOX-based or other chemo for BC. Pts will be randomized to either oral minocycline or placebo for up to a 1 week loading period plus chemo treatment period and an optional subsequent 2 week period. Eligibility Criteria: Women diagnosed with BC stages I-III initiating first line adjuvant or neoadjuvant chemo. Aims: (1) to evaluate symptoms related to anxiety and depression and cognitive changes during and after chemo completion (2) to evaluate markers of neuro inflammation as assessed by blood based inflammatory cytokines and central markers of inflammation and microglia activation using 1 F-Fludeoxyglucose and 11C-PK11195 positron emission tomography. Primary endpoints are changes in Center for Epidemiological Studies Depression Scale (CES-D) and State Trait Anxiety Index (STAI) from baseline to end of study after minocycline vs placebo intervention. Secondary endpoints are changes in cognitive function during chemo using validated cognitive testing including N-Back Test, Behavioural Rating Inventory of Executive Function (BRIEF) and the Multifactorial Memory Questionnaire Ability Scale (MMQ). Statistical Methods: Primary analysis for efficacy will be intention-to-treat. The main objective is to preliminarily evaluate the effect of minocycline on chemo-induced depressive symptoms in terms of changes in CES-D and STAI scores. Mixed models will be used to evaluate cognitive function changes. A sample size of 23 per group, will give 80% power to detect an effect size of 0.74 standard deviation (SD) difference between the 2 groups at significance level of 0.10 based on a 2 sided two-sample t-test. From our experience, attrition of less than 20% is expected for studies in this patient population in our center, and to account for this, we plan to recruit up to 60 patients. 16 of 46 evaluable pts have been accrued to date. Accrual started in January 2016. Funded by Pelotonia grant from The OSUCCC. Contact: Study PI: Maryam.lustberg@osumc.edu

Citation Format: Boutrid H, Reinbolt R, Knopp M, Williams N, VanDeusen J, Sardesai S, Noonan A, Flora L, Gleich E, Pan X, Berger M, Vargo C, Wesolowski R, Ramaswamy B, DeVries AC, Lustberg M. Does minocycline mitigate chemotherapy induced neuroinflammation? A phase II randomized placebo controlled study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-05-03.

Abstract P5-08-06: Impact of a decision-support tool on the utilization of colony-stimulating factors and incidence of febrile neutropenia among patients with breast cancer

Background:

Following the 2012 American Society of Clinical Oncology's Choosing Wisely campaign recommendation against the routine use of colony-stimulating factors (CSFs) for the primary prevention of febrile neutropenia (FN) in patients with ≤ 20% risk, an evidence-based clinical decision-support tool (CSF decision tool) was implemented to promote risk-appropriate CSF use in breast cancer patients receiving chemotherapy by a national payer in the United States (US). We hypothesized that there should be no change in pre- and post-implementation FN rates if the CSF decision tool had promoted appropriate FN risk stratification among breast cancer patients.

Methods:

A retrospective observational cohort study design was used to analyze data from a national payer administrative claims database of nearly 40 million lives geographically spread across the US. The CSF decision tool was first implemented in 2014, with a staggered implementation across states (July 1, 2014 - November 1, 2014). Study subjects were female patients, aged ≥ 18 years, who initiated chemotherapy for breast cancer in the time periods before or after the implementation of the decision tool (July 1, 2014 through March 30, 2015). Patients were assigned to case (defined as patients in the states where the CSF decision tool had been implemented) or control (defined as patients in states where the CSF decision tool had yet to be implemented) cohort. Patients in each cohort were followed up to 6 months after the first chemotherapy dose in the pre- and post-implementation periods. The outcomes were changes in the incidence of FN and CSF use rates, respectively. Rates of FN and CSF use were compared between the cohorts using difference-in-differences models; generalized estimating equations were used to adjust for differences in baseline risk factors including age, history of neutropenia or infections.

Results:

The final study population comprised 7,224 patients: 4,001 and 3,223 in the case and control cohorts, respectively. There was a higher proportion of patients who were 65 years or older in the case cohort compared to the control (22% vs 18%, p: <0.001). Otherwise, the cohorts were comparable in FN risk factors at baseline in pre- and post-implementation periods.

In adjusted regression results, pre- and post-implementation FN rates were not significantly different for both case (5.38% to 5.65%) and control (5.07% to 5.13%) cohorts, [p=0.778]. Use of CSF in the pre- and post-implementation periods decreased from 75% to 69% in the case cohort compared with a reduction from 72% to 71% in the control cohort: an absolute difference of 5.4% decrease in CSF use associated with the implementation of the decision support tool [p= 0.006].

Conclusion:

Despite a modest reduction in CSF use, we found no evidence of an increase in FN rates after the implementation of the CSF decision tool. Given the lack of impact of the Choosing Wisely campaign on inappropriate CSF use; our findings suggest that beyond the educational efforts and media campaigns, a greater reduction in unnecessary CSF use can be achieved through the use of clinical decision algorithms to reduce practice variation and improve adherence to national guideline recommendations.

Citation Format: Adeboyeje G, Agiro A, Goodwin A, DeVries A, Malin J. Impact of a decision-support tool on the utilization of colony-stimulating factors and incidence of febrile neutropenia among patients with breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-06.

Social stress exacerbates stroke outcome by suppressing Bcl-2 expression

The relationship between stressful life events and the onset of disease is well documented. However, the role of psychological stress as a risk factor for life-threatening cerebrovascular insults such as stroke remains unspecified, but could explain individual variation in stroke outcome. To discover the mechanisms through which psychological stress may alter stroke outcome, we modeled the effects of chronic social intimidation and stress on ischemia-induced bcl-2 expression and early neuronal cell loss resulting from cerebral artery occlusion in mice (C57BL/6). The bcl-2 protooncogene promotes cell survival and protects against apoptosis and cellular necrosis in numerous neurodegenerative disorders, including stroke. In our study, male mice were chronically exposed to aggressive social stimuli before induction of a controlled, mild ischemic insult. Stressed mice expressed approximately 70% less bcl-2 mRNA than unstressed mice after ischemia. In addition, social stress greatly exacerbated infarct in wild-type mice but not in transgenic mice that constitutively express increased neuronal bcl-2. Despite similar postischemic concentrations of corticosterone, the major stress hormone in mice, high corticosterone concentrations were significantly correlated with larger infarcts in wild-type mice but not bcl-2 transgenic mice. Thus, enhanced bcl-2 expression offsets the potentially deleterious consequences of high postischemic plasma corticosterone concentrations. Taken together, these data demonstrate that stressful prestroke social milieu strongly compromises an endogenous molecular mechanism of neuroprotection in injured brain and offer a new behavioral target for stroke therapy.

Cognitive and behavioral assessment in experimental stroke research: will it prove useful?

Stroke in humans is associated with deficits in sensorimotor and cognitive function. Consequently, many stroke researchers recently have expanded their techniques to assess cognitive and behavioral correlates of histologically-determined stroke damage in animal models. Although the incorporation of functional outcome assessment represents an important step forward in stroke research, reports of middle cerebral artery occlusion (MCAO) induced behavioral deficits often conflict, and a significant correlation between post-stroke histology and behavior has been reported in few stroke studies. Discrepancies in behavioral outcomes among studies may be due to several factors, such as method of MCAO, duration of occlusion, strain, the timing and method of the behavioral testing and the laboratory environment. Furthermore, proper experimental and control groups, necessary to rule out potential confounding factors during cognitive testing, often are not incorporated. The goal of this review is: (1) to provide a description of the techniques most commonly employed to assess functional outcome after (MCAO) in rodents and (2) to identify potential confounding factors that may interfere with a clear interpretation of the behavioral data.

Targeted reduction of oxytocin expression provides insights into its physiological roles

Oxytocin is a nonapeptide hormone that participates in the regulation of parturition and lactation. It has also been implicated in various behaviors, such as mating and maternal, and memory. To investigate whether or not oxytocin (OT) is essential for any of these functions, we eliminated, by homologous recombination, most of the first intron and the last two exons of the OT gene in mice. Those exons encode the neurophysin portion of the oxytocin preprohormone which is hypothesized to help in the packaging and transport of OT. The homozygous mutant mice have no detectable neurophysin or processed oxytocin in the paraventricular nucleus, supraoptic nucleus or posterior pituitary. Interestingly, homozygous mutant males and females are fertile and the homozygous mutant females are able to deliver their litters. However, the pups do not successfully suckle and die within 24 hours without milk in their stomachs. OT injection into the dams or rescue with the rat OT gene restores the milk ejection in response to suckling. OT is also needed for post-partum alveolar proliferation. These results indicate an absolute requirement for oxytocin for successful milk ejection, but not for mating, parturition and milk production, in mice. Furthermore, homozygous mutant mice show reduced aggression in some tests.

Anticonvulsant lamotrigine administered on reperfusion fails to improve experimental stroke outcomes

BACKGROUND AND PURPOSE

Recent results suggest that selective inhibitors of presynaptic neuronal ion channels can diminish glutamate release during cerebral ischemia and modulate excitotoxic cell death. The aim of the present study was to evaluate lamotrigine (LTG), an antiepileptic that inhibits presynaptic sodium and voltage-sensitive calcium channels, as a potential stroke resuscitation agent in the rat. Three dosages of LTG were examined for effect on infarction volume and sensorimotor behavioral recovery after middle cerebral artery (MCA) occlusion.

METHODS

Halothane-anesthetized male Wistar rats were subjected to 2 hours of MCA occlusion by the intraluminal occlusion technique. Physiological variables were controlled, and ipsilateral cortical perfusion was monitored by laser Doppler flowmetry throughout ischemia. At onset of reperfusion, rats received intravenous LTG 5, 10, or 20 mg/kg or PBS (n=9 to 11 per group) during 15 minutes. Behavioral assessment was completed at 3 and 7 days after stroke, and the brain was harvested for histology (triphenyltetrazolium chloride staining).

RESULTS

Values are mean+/-SE. Cortical infarction volumes were unchanged in LTG-treated animals: 14+/-6% of contralateral cortex at 5 mg/kg LTG, 17+/-7% at 10 mg/kg, and 30+/-6% at 20 mg/kg, versus saline-treated cohorts (12+/-3%; P:=0.19; n=9). Caudate-putamen infarction injury was also unchanged (37+/-11% of contralateral caudate-putamen at 5 mg/kg LTG, 44+/-8% at 10 mg/kg, and 65+/-9% at 20 mg/kg versus saline (38+/-11%; P:=0.18). Total infarction was not different among groups (P:=0.15). Consistent with histology, behavioral outcomes were unimproved by treatment.

CONCLUSIONS

Histological damage and behavioral recovery at 7 days after MCA occlusion was not altered by LTG treatment over the dosage range used in the present study.

How successful are oncologists in identifying patient distress, perceived social support, and need for psychosocial counselling?

20-40% of cancer patients show emotional distress. Psychosocial support should be offered to severely distressed patients. However, little is known about the selection of patients to whom such support should be offered. This study investigated oncologists' ability to identify such patients. In a consecutive series of 298 cancer patients undergoing radiotherapy, distress, perceived social support and desire for supportive counselling were assessed using screening instruments. Simultaneously, 8 oncologists estimated patient distress and need for psychosocial support. A complete set of data was obtained in 80.2% of cases. Concordance of the oncologists' estimation of patient distress and perceived social support with the results of the screening instruments was weak (kappa = 0.10 and kappa = 0.05). Oncologists recognized the presence of severe distress only in 11 of the 30 severely distressed patients. Correct perception of distress was lower in patients with head and neck cancer and lung cancer and in lower class patients. Oncologists' recommendations for supportive counselling did not correlate with patient distress or the amount of perceived support but rather with progressive disease and less denial behaviour. Our results underline the need for educating oncologists in order to improve their ability to identify patient distress.

[Perfusion-index values evaluated by dynamic magnetic resonance imaging in advanced rectal carcinoma. A new predictor of response to preoperative radiochemotherapy?]

PURPOSE

The aim of our study was to evaluate in vivo the influence of tumor microcirculation data on therapy outcome.

PATIENTS AND METHODS

Tumor perfusion data of primary rectal carcinoma (n = 14, cT3) who underwent preoperative chemoradiation have been analyzed (Table 1). The perfusion data were acquired at the beginning and at the end of therapy by use of an ultrafast T1-mapping sequence on a whole-body magnetic resonance imager. The gadolinium-DTPA concentration-time-curves were evaluated for arterial blood and tumor before, during and after intravenous constant rate infusion and from that the perfusion index (PI) was calculated. Subsequent resection of the tumors allowed for a correlation of perfusion index values with the pathological classification.

RESULTS

Nine patients showed a T downstaging (ypT0-2, group 1), 5 patients did not (ypT3, group 2). The initial mean perfusion index value of group 1 (n = 9) was 8.2 ml/min/100 g (+/- 2) and for group 2 (n = 5) 10.4 ml/min/100 g (+/- 0.4). The difference in perfusion index values before chemoradiation between group 1 and group 2 was significant different (p = 0.012, Mann-Whitney test). The perfusion index value at the end of therapy of group 1 (n = 6) was 9.6 ml/min/100 g (+/- 2.8) and for group 2 (n = 4) 10.7 ml/min/100 g (+/- 1.6). The difference in perfusion index values after chemoradiation between group 1 and group 2 was not significant different (Table 2).

CONCLUSION

Our used perfusion index value combines 2 parameters: tumor perfusion and extraction fraction. Therefore a significant negative influence on therapy outcome of high perfusion index values could be explained possibly by areas with a high portion of high perfusion (e.g. av-shunts) and a low extraction fraction (= low exchange of nutrients). However, we could show a significant negative influence of high perfusion index values on therapy outcome (p = 0.012). Because the tumor stage has a significant influence on tumor-free survival, there is a possibility for using initial perfusion index values as a new prognostic factor in rectal carcinoma without sphincter infiltration undergoing a preoperative chemoradiation. To examine this hypotheses a prospective trial is in preparation.

Use of complementary and alternative medicine by cancer patients is not associated with perceived distress or poor compliance with standard treatment but with active coping behavior: a survey

BACKGROUND

Complementary and alternative medicine (CAM) is often used by cancer patients. Data on characteristics of users, concomitant psychologic disturbance, and compliance with standard treatment continue to be controversial. Use of and interest in CAM and their correlation with psychologic disturbance, ways of coping with illness, and compliance with standard treatment were examined in this study.

METHODS

The authors conducted a survey in a consecutive sample of 205 cancer patients undergoing radiotherapy, using a structured questionnaire to record use of and interest in CAM, the Hospital Anxiety and Depression Scale, the Hornheide Questionnaire to assess patient distress and social support, and the Freiburg Questionnaire of Coping with Illness.

RESULTS

Of the 172 participants, 24.4% (response rate, 83.9%) reported use of CAM, and 31.4% reported not having used but being interested in such methods. Logistic regression analysis including clinical, demographic, and psychologic characteristics as independent variables yielded 3 predictors of use of or interest in CAM: younger age (P = 0.004; odds ratio (OR), 0.96), progressive cancer (P = 0.064; OR, 1.47), and active coping behavior (P = 0.016; OR, 1.65). Patients interested in or using CAM did not show more psychologic disturbance, poorer social support, or less trust in medicine or compliance with radiotherapy than subjects without such interest.

CONCLUSIONS

Use of CAM by cancer patients is not associated with perceived distress or poor compliance with medical treatment but with active coping behavior. Patients seem to consider CAM as supplementary to standard medical methods and one way of avoiding passivity and of coping with feelings of hopelessness.

Cognitive deficits after focal cerebral ischemia in mice

BACKGROUND AND PURPOSE

The interpretation of cognitive data in many experimental stroke studies is problematic because middle cerebral artery occlusion (MCAO) is associated with sensorimotor alterations that may become confounding factors in cognitive testing. The purpose of the current study was to determine if it is possible to measure MCAO-induced cognitive deficits by using short durations of ischemia that do not result in alterations in sensorimotor behavior in mice.

METHODS

Male C57/Bl6 mice were subjected to 60 or 90 minutes of intraluminal MCAO or sham surgery. In the first cohort of animals (n=12/group), locomotor activity, balance, and coordination were evaluated 2 weeks after surgery. In a second cohort of animals (n=10/group), the effects of 60 minutes of MCAO on subsequent learning and memory were assessed with a step-down passive avoidance task beginning 1 week after surgery. In a third cohort of animals (n=8 to 10/group), training in a passive avoidance task was completed before 60 minutes of MCAO, then retention of the task was assessed 1 week after surgery. In all animals, infarction size was determined after 14 days of reperfusion with use of cresyl violet staining and quantitative image analysis.

RESULTS

There was no significant difference in infarction volume in the cerebral cortex or caudoputamen after 60 versus 90 minutes of MCAO. However, there was a significant increase in latency to move 1 body length in the 90-minute MCAO group compared with the 60-minute MCAO and sham groups. In 2 additional cohorts of animals, 60-minute MCAO was associated with a deficit in the acquisition and retention of a passive avoidance task regardless of whether the task training occurred before or after MCAO.

CONCLUSIONS

Long-term cognitive deficits can be induced in mice by using a short duration of MCAO (60 minutes) that does not result in concomitant sensorimotor deficits.

sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl)-piperidine affords neuroprotection from focal ischemia with prolonged reperfusion

BACKGROUND AND PURPOSE

We previously showed that the intravenous administration of the potent final sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl)-piperidine (PPBP) provides neuroprotection against transient focal cerebral ischemia and that the protection depends on treatment duration. We tested the hypothesis that PPBP would provide neuroprotection in a model of transient focal ischemia and 7 days of reperfusion in the rat as assessed with neurobehavioral outcome and infarction volume.

METHODS

Under the controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 hours of middle cerebral artery occlusion (MCAO) with the intraluminal suture occlusion technique. We used laser Doppler flowmetry to assess MCAO. At 60 minutes after the onset of ischemia, rats were randomly assigned to 1 of 4 treatment groups in a blinded fashion and received a continuous intravenous infusion of control saline or 0.1, 1, or 10 micromol. kg(-1). h(-1) PPBP for 24 hours. Neurobehavioral evaluation was performed at baseline (3 to 4 days before MCAO) and at 3 and 7 days of reperfusion. Infarction volume was assessed with triphenyltetrazolium chloride staining on day 7 of reperfusion in all rats.

RESULTS

Triphenyltetrazolium chloride-determined infarction volume of ipsilateral cortex was smaller in rats treated with 10 micromol. kg(-1). h(-1) PPBP (n=15, 68+/-12 mm(3), 18+/-3% of contralateral structure, P<0.05) (mean+/-SEM) compared with corresponding rats treated with saline (n=15, 114+/-11 mm(3), 31+/-3% of contralateral structure). PPBP did not provide significant neuroprotection in the caudoputamen complex. Although MCAO was associated with several alterations in behavior, the treatment with PPBP had no effect on behavioral outcomes.

CONCLUSIONS

The data demonstrate that the potent final sigma(1)-receptor ligand PPBP decreases cortical infarction volume without altering neurobehavior after transient focal ischemia and prolonged reperfusion in the rat.

The effects of oxytocin and vasopressin on partner preferences in male and female prairie voles (Microtus ochrogaster)

This study compared the effects of centrally administered oxytocin (OT) and arginine vasopressin (AVP) on partner preference formation and social contact in male and female prairie voles (Microtus ochrogaster). After 1 hr of cohabitation and pretreatment with either AVP or OT, both males and females exhibited increased social contact and significant preference for the familiar partner. After pretreatment with either an OT receptor antagonist (OTA) or an AVP (V1a) receptor antagonist (AVPA), neither OT nor AVP induced a partner preference. In addition, treatment with OT+OTA or AVP+AVPA was associated with low levels of social contact in both sexes. Either AVP or OT is sufficient to facilitate social contact if either the OT or AVP receptor is available. However, the formation of partner preferences may require access to both AVP and OT receptors.

Lipopolysaccharide facilitates partner preference behaviors in female prairie voles

Exposure to proinflammatory cytokines (e.g., IL-1beta) or lipopolysaccharide (LPS) produces an acute activation of the immune response and results in a repertoire of behavioral patterns collectively termed sickness behaviors. Although nonspecific responses to pathogenic infection have traditionally been viewed as maladaptive effects of infection, sickness behaviors may have significant, adaptive value for the host. One set of adaptive behaviors affected by infection among mammals and birds is mate choice. In Experiment 1, female prairie voles exhibited the expected increase in blood corticosterone concentrations in response to a 0.1 cc i.p. LPS injection (50 microg), indicating activation of the endocrine system. A separate cohort of females was injected with LPS or saline and paired for 6 h with a novel, previously unpaired male. Following the cohabitation period, LPS-injected females spent significantly more time (p < 0.05) with the familiar partner when given a choice between familiar and unfamiliar males in a three-chamber apparatus designed to test partner preferences. Saline-injected females spent significantly more time with the unfamiliar male. In Experiment 2, males injected with LPS or saline spent equal amounts of time with familiar and unfamiliar females following a 6 h cohabitation with a naive female, and therefore, did not exhibit preferences. From a proximate perspective, this study provides evidence that sickness behaviors influence female, but not male, partner preference in prairie voles.

The effects of oxytocin and vasopressin on partner preferences in male and female prairie voles (Microtus ochrogaster)

This study compared the effects of centrally administered oxytocin (OT) and arginine vasopressin (AVP) on partner preference formation and social contact in male and female prairie voles (Microtus ochrogaster). After 1 hr of cohabitation and pretreatment with either AVP or OT, both males and females exhibited increased social contact and significant preference for the familiar partner. After pretreatment with either an OT receptor antagonist (OTA) or an AVP (V1a) receptor antagonist (AVPA), neither OT nor AVP induced a partner preference. In addition, treatment with OT+OTA or AVP+AVPA was associated with low levels of social contact in both sexes. Either AVP or OT is sufficient to facilitate social contact if either the OT or AVP receptor is available. However, the formation of partner preferences may require access to both AVP and OT receptors.

Proton radiation therapy for chordomas and chondrosarcomas of the skull base

OBJECT

Local tumor control, patient survival, and treatment failure outcomes were analyzed to assess treatment efficacy in 58 patients in whom fractionated proton radiation therapy (RT) was administered for skull base chordomas and chondrosarcomas.

METHODS

Between March 1992 and January 1998, a total of 58 patients who could be evaluated were treated for skull base tumors, 33 for chordoma and 25 for chondrosarcoma. Following various surgical procedures, residual tumor was detected in 91% of patients; 59% demonstrated brainstem involvement. Target dosages ranged from 64.8 and 79.2 (mean 70.7) Co Gy equivalent. The range of follow up was 7 to 75 months (mean 33 months). In 10 patients (17%) the treatment failed locally, resulting in local control rates of 92% (23 of 25 patients) for chondrosarcomas and 76% (25 of 33 patients) for chordomas. Tumor volume and brainstem involvement influenced control rates. All tumors with volumes of 25 ml or less remained locally controlled, compared with 56% of tumors larger than 25 ml (p = 0.02); 94% of patients without brainstem involvement did not experience recurrence; in patients with brainstem involvement (and dose reduction because of brainstem tolerance constraints) the authors achieved a tumor control rate of 53% (p = 0.04). Three patients died of their disease, and one died of intercurrent disease. Actuarial 5-year survival rates were 100% for patients with chondrosarcoma and 79% for patients with chordoma. Grade 3 and 4 late toxicities were observed in four patients (7%) and were symptomatic in three (5%).

CONCLUSIONS

High-dose proton RT offers excellent chances of lasting tumor control and survival, with acceptable risks. In this series all small- and medium-sized tumors with no demonstrable brainstem involvement have been controlled; all such patients are alive. Surgical debulking enhanced delivery of full tumoricidal doses, but even patients with large tumors and disease abutting crucial normal structures benefited.

[The role of radiotherapy in the treatment of malignant meningiomas]

PURPOSE

Most malignant meningiomas will recur following surgical resection only. The role of irradiation and radiation dose levels is poorly defined. This study reviews a single institution experience using both, conventional and high doses > or = 60 Gy/CGE radiation regimen.

PATIENTS AND METHODS

Between 1974 and 1995 16 patients with histologically proven malignant meningioma underwent radiation therapy (RT). Age at diagnosis ranged between 6 and 79 years (median: 49 years). Three patients reported previous irradiation to the head at least 14 years prior to diagnosis. Ten patients were treated for primary, and 6 patients for recurrent disease. Six patients underwent gross total and 10 patients subtotal resection (Table 1). RT was delivered using conventional, megavoltage photons or combined 160 MeV proton and photon irradiation. Except 1 patient, who died during RT, the radiation doses ranged between 40 and 70 Gy/CGE (= Cobalt Gray Equivalent) (median: 58 Gy/CGE, Table 2).

RESULTS

With median observation time of 59 months (range: 10 to 155 months), actuarial local control rates at 5 and 8 years were 52% and 17%, respectively. Target doses > or = Gy/CGE resulted in significantly improved tumor control (100%) compared to < 60 Gy/CGE (17%) (p = 0.0006, Table 3 and Figure 1). Improved local control translated also in increased overall survival: 87% (> or = 60 Gy/CGE) versus 15% (< 60 Gy/CGE) at 5 years (p = 0.025, Figure 2). At time of analysis, 6/16 patients (38%) were alive. Two patients developed symptomatic brain damage at doses of 59.3 and 72 Gy/CGE.

CONCLUSION

Conformal, radiation therapy with target doses > or = 60 Gy/CGE, in this study by use of combined proton and photon irradiation, can significantly improve chances of long-term local control and survival for patients diagnosed with these challenging tumors.

Neurobehavioral deficits in mice lacking the erythrocyte membrane cytoskeletal protein 4.1

The erythrocyte membrane cytoskeletal protein 4.1 (4.1R) is a structural protein that confers stability and flexibility to erythrocytes via interactions with the cytoskeletal proteins spectrin and F-actin and with the band 3 and glycophorin C membrane proteins. Mutations in 4.1R can cause hereditary elliptocytosis, a disease characterized by a loss of the normal discoid morphology of erythrocytes, resulting in hemolytic anemia [1]. Different isoforms of the 4.1 protein have been identified in a wide variety of nonerythroid tissues by immunological methods [2-5]. The variation in molecular weight of these different 4.1 isoforms, which range from 30 to 210 kDa [6], has been attributed to complex alternative splicing of the 4.1R gene [7]. We recently identified two new 4.1 genes: one is generally expressed throughout the body (4. 1G) [8] and the other is expressed in central and peripheral neurons (4.1N) [9]. Here, we examined 4.1R expression by in situ hybridization analysis and found that 4.1R was selectively expressed in hematopoietic tissues and in specific neuronal populations. In the brain, high levels of 4.1R were discretely localized to granule cells in the cerebellum and dentate gyrus. We generated mice that lacked 4.1R expression; these mice had deficits in movement, coordination, balance and learning, in addition to the predicted hematological abnormalities. The neurobehavioral findings are consistent with the distribution of 4.1R in the brain, suggesting that 4.1R performs specific functions in the central nervous system.

Comparison of chromosome telomere integrity in multiple tissues from subjects at different ages

Telomere DNA, at the ends of each chromosome, is conserved in nature and required for chromosome replication and stability. Reduction in telomere length has been observed in several malignancies as well as in leukocytes from healthy persons with advancing age. There is a paucity of data regarding telomere length and the effects of in vivo aging in different tissues. These data could be helpful in interpreting telomere length and understanding the role of telomere integrity and telomerase activity in malignant cells. We report telomeric DNA integrity studies of blood and skin collected from eight Caucasians of both sexes representing each decade of life from the fetus to 72 years of age without exposure to chemotherapy or radiation. In addition, telomeric data from 15 other tissues from the fetus and 8 other tissues from the 72-year-old male were examined. No significant differences were found in the shortest telomere size, the average telomere size, or telomere size variation between blood and skin from subjects at different ages. The average telomere size was 11.7 +/- 2.2 kb for blood and 12.8 +/- 3.7 for skin in all subjects studied. The shortest telomere length was 5.4 +/- 1.9 kb for blood and 4.3 +/- 0.9 kb for skin. Significant differences (P < 0.001) were found in the overall length of the DNA hybridization signal representing the shortest telomere size and the length of the DNA peak migration hybridization signal representing variation in telomere size between the 20-week fetus and the 72-year-old male. The 72-year-old male showed the shortest telomeres and the most variation (heterogeneity) in telomere size for all tissues studied, but the greatest differences were observed in blood compared with other tissues (e.g., average telomere length was 12.2 kb in the fetus and 7.2 kb in the 72-year-old male). The size of the telomere was negatively correlated with age for all tissues studied.

Pharmacokinetic MRI for assessment of malignant glioma response to stereotactic radiotherapy: initial results

The purpose of this study was to assess the value of dynamic, contrast-enhanced MRI in patients with malignant glioma (a) to predict before stereotactic radiotherapy local tumor control, (b) to investigate temporal changes in tumor microcirculation after stereotactic radiotherapy, and (c) to analyze whether malignant glioma response may be predicted earlier by alterations in the tissue pharmacokinetics rather than in terms of tumor volume. Ninety MRI studies were performed of 18 patients with malignant glioma before and 6, 18, 26, 52, and 72 weeks after the end of stereotactic radiotherapy. The signal time courses of the contrast-enhanced tumors were analyzed using a pharmacokinetic two-compartment model that calculates for the parameter A, reflecting the degree of MRI signal enhancement [no units] and the exchange rate constant k21 [min(-1)]. Before radiotherapy, the amplitude A was significantly (P < .05) lower in patients with subsequent local tumor control (n = 8; mean A = .34 +/- .15) compared to patients without subsequent local tumor control (n = 10; mean A = .94 +/- .71). In the local tumor control group, early after stereotactic radiotherapy (at 6-18 weeks), there was a significant (P < .05) time-dependent decrease in the parameter k21, whereas there was still no alteration in the tumor volume. A low amplitude A before radiotherapy, combined with an early drop of k21 after stereotactic radiotherapy, reliably characterized the group of patients with subsequent tumor volume decrease. Our preliminary results suggest that two contrast-enhanced dynamic MR studies, one before and one early after stereotactic radiotherapy, offer important information on local tumor control within the first 6 to 18 weeks after stereotactic radiotherapy. Moreover, this response may be evidenced before tumor volume changes and provides a therapeutic window to broaden treatment options and to improve treatment outcome.

Conditioned increases in anxiogenic-like behavior following exposure to contextual stimuli associated with cocaine are mediated by corticotropin-releasing factor

Although cocaine is a powerful reinforcer, it has been reported to produce anxiety in humans and anxiogenic-like behavior in animals. The goal of this study was three-fold: (1) to determine the doses of cocaine that induce anxiogenic-like behavior in the elevated plus-maze in rats, (2) to determine if cocaine-associated contextual cues are capable of eliciting anxiogenic-like behavior in the absence of the drug, and (3) to identify possible mechanisms through which cocaine-associated cues affect behavior in the elevated plus-maze. Measurement of the amount of time that the animals spend exploring the open arms of the maze provides a sensitive index of anxiogenic-like behavior in rats. In experiment 1, rats were injected with 10 mg/kg, 20 mg/kg, or 30 mg/kg cocaine HCl or saline for 6 days. On day 6, the rats were tested in the elevated plus-maze 25 min after injection with cocaine or saline. The animals chronically treated with the three doses of cocaine exhibited a dose-dependent increase in anxiogenic-like behavior in the elevated plus-maze, compared to the saline-treated group. In experiment 2, cocaine-induced (30 mg/kg) conditioning was achieved using a simple contextual design. On the final day of the experiment (day 6), after 5 days of conditioning, the rats were exposed for 25 min to the cocaine-associated contextual cues, then placed in the elevated plus-maze. Animals that had been exposed to cocaine-associated contextual cues prior to being placed in the elevated plus-maze exhibited a significant increase in anxiogenic-like behavior compared to the control groups. However, pretreatment of the rats with the CRF antagonist, alpha-helical CRF9-41 (1 microg, i.c.v.), on the test day, prior to exposure to cocaine-associated contextual cues, attenuated the subsequent anxiogenic-like behavioral response in the elevated plus-maze (experiment 3). The results suggest that contextual cues associated with repeated treatment with 30 mg/kg cocaine are capable of eliciting anxiogenic-like behavior in the absence of the drug and that CRF mediates the expression of anxiogenic-like behaviors in the elevated plus-maze following exposure to cocaine-associated cues. The conditioned anxiogenic action elicited by cocaine-associated cues may have relevance for understanding the complex addictive nature of this drug and some of the clinical phenomena related to its use.

Lectin intravital perfusion studies in tumor-bearing mice: micrometer-resolution, wide-area mapping of microvascular labeling, distinguishing efficiently and inefficiently perfused microregions in the tumor

Intravital lectin perfusion was combined with computer-guided scanning digital microscopy to map the perfused elements of the vasculature in tumor-bearing mice. High-precision composite images (spatial precision 1.3 micron and optical resolution 1.5 micron) were generated to permit exact positioning, reconstruction, analysis, and mapping of entire tumor cross-sections (c. 1 cm in diameter). Collation of these mosaics with nuclear magnetic resonance maps in the same tumor plane identified sites of rapid contrast medium uptake as tumor blood vessels. Digitized imaging after intravital double labeling allowed polychromatic visualization of two different types of mismatched staining. First, simultaneous application of two lectins, each bearing a different fluorochrome, revealed organ-specific differential processing in the microvascular wall. Second, sequential application of two boluses of one lectin, bearing different fluorochromes successively, distinguished between double-labeled microvessels, representing efficiently perfused vascular segments, and single-labeled microvessels, with inefficient or intermittent perfusion. Intravital lectin perfusion images of blood vessels in the vital functional state thus highlighted biologically significant differences in vessel function and served as high-resolution adjuncts to MR imaging.

Ketoconazole in the prevention of acute respiratory distress syndrome

We conducted a critical review of the literature on ketoconazole in preventing acute respiratory distress syndrome (ARDS), a serious disorder associated with high mortality. Two double-blind, prospective, placebo-controlled, randomized trials compared ketoconazole with placebo for prophylaxis of ARDS. In one trial, compared with placebo, ketoconazole resulted in a reduced frequency of ARDS (6% vs 31%, p<0.01), lower plasma thromboxane B2 levels (33 vs 75 pg/ml, p<0.05), and shorter intensive care unit stay (7 vs 15.5 days, p<0.05). In the second trial the drug reduced the frequency of ARDS (15% vs 64%, p=0.002), lowered thromboxane B2 levels (83 vs 143 pg/ml), and reduced mortality (15% vs 39%, p=0.05) compared with placebo. Larger multicenter studies are warranted to validate the findings of these two trials.

Conditioned release of corticosterone by contextual stimuli associated with cocaine is mediated by corticotropin-releasing factor

Elevated blood concentrations of corticosterone (CORT), an adrenal steroid associated with stress responses, is one of the endocrine correlates of cocaine treatment. Experiment 1 confirmed and extended previous findings that chronic cocaine treatment does not alter corticosteroid responses to cocaine. In Experiment 2, conditioned endocrine effects of cocaine were examined in three groups of rats after 7 consecutive days of treatment. Cocaine-induced conditioning was achieved using a simple contextual design. In group 1 (paired), rats were injected with cocaine (30 mg/kg), then immediately placed into a locomotor activity chamber for 30 min. One hour after the rats were returned to their home cages, they received an injection of saline. In group 2 (unpaired), rats were injected with saline, then immediately placed into a locomotor activity chamber for 30 min. One hour after the rats were returned to their home cages, they received an injection of cocaine (30 mg/kg). Rats in group 3 (control) received only saline injections, but otherwise were treated as animals in the other treatment groups. On the test day (Day 8), all rats were placed immediately into the locomotor apparatus for 30 min prior to collection of a blood sample. Blood CORT concentrations and locomotor activity in the paired group were significantly higher than in the unpaired and control groups. However, pretreatment of the rats in Experiment 3 with the corticotropin-releasing factor (CRF) antagonist, alpha-helical CRF9-41 (1 microg, i.c.v.), on the test day, prior to exposure to cocaine-associated contextual cues, attenuated the subsequent conditioned increase in blood CORT concentrations. These data represent the first demonstration of classical conditioning of a steroid hormone response to stimuli associated with a psychoactive drug in rats and suggest that the effect is mediated by endogenous CRF. Because the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in modulating the actions of cocaine, it is plausible that such conditioned increases in CORT release by cocaine-associated cues may further predispose an organism to the reinforcing effects of the drug or enhance the susceptibility to drug-taking behavior. Alternatively, such conditioned effects may be related to the anxiogenic properties of cocaine. Further understanding of the conditioned effects of hormones in the development and expression of addictive behaviors may provide new insights into treatment of drug addiction.

Do specialists order too many tests? The case of allergists and pediatric asthma

BACKGROUND

Is the practice style of specialists overly reliant on diagnostic tests? Health maintenance organization managers and other clinicians have been critical of the high cost practice styles of specialists, but if the specialists' practice style ultimately results in similar or lower total costs because of better outcomes in the treatment of exceptional cases, then such practice styles are cost-effective and should be encouraged. Indeed, if this is the case, not employing a test-intensive practice style could be considered negligent under a legal criterion.

OBJECTIVE

We attempted to determine whether the care of pediatric asthmatic patients by allergists is characterized by more testing, but by better, less costly outcomes than care by non-allergists.

METHODS

We used administrative data on pediatric asthmatic cases from a large health care plan from 1992 to determine whether patients treated by allergists received more tests, cost more, and had fewer asthmatic management breakdowns than patients treated by non-allergists. We used regression analysis to hold constant aspects of the patient's case mix.

RESULTS

Although allergists ordered significantly more tests than non-allergists, their overall treatment costs were similar. Patients treated by allergists had fewer management breakdowns.

CONCLUSIONS

These results suggest that the allergists' test-intensive practice style is cost-effective.

Stress affects corticosteroid and immunoglobulin concentrations in male house mice (Mus musculus) and prairie voles (Microtus ochrogaster)

Glucocorticoids, secreted in response to perceived stress, can suppress immunoglobulin (Ig) levels and compromise immune function in mice and rats. Prairie voles (Microtus ochrogaster) have been reported to exhibit basal corticosterone concentrations that would cause pathological changes in the immune function of most other rodents. The goals of the present study were to verify that serum corticosterone concentrations are high in prairie voles, as compared with house mice (Mus musculus), by measuring serum corticosterone with the same RIA; to examine the effects of mild stressors on corticosterone response in both species and to examine the effects of elevated corticosterone levels on IgM and IgG levels in prairie voles and house mice. After 2 weeks of randomly timed 15-min daily restraint or cold-water swim sessions, animals were injected with sheep red blood cells. The data confirmed that basal blood concentrations of corticosterone were higher in prairie voles than house mice, but these high levels doubled after the first swim session in prairie voles, indicating that the adrenals can respond to stressors by producing increased corticosterone. After stress, antibody production (both IgM and IgG) was reduced in house mice but not in prairie voles, despite higher blood concentrations of glucocorticoids in prairie voles. Although body mass was statistically equivalent between species, prairie voles and mice differed dramatically in adrenal and splenic masses. Average adrenal mass of prairie voles was approximately three times the average mass of these organs in house mice; in contrast, the average splenic mass of house mice was approximately three times that of prairie voles. These data may be relevant to seasonal changes in immune function and survival.

Effects of photoperiod and 2-deoxy-D-glucose-induced metabolic stress on immune function in female deer mice

Nontropical rodents may experience large fluctuations in both food availability and energetic demands. The energy required for thermoregulation is high during the winter when energy availability is usually low. Winter conditions can induce a state of energetic stress that elevates circulating glucocorticoid levels and compromises immune function. Exposure to short days enhances immune function; the adaptive function of short-day enhancement of immune function may be to counteract the effects of stress-induced immunocompromise. To examine the role of energy availability in immune function, female deer mice were housed in either long (16:8-h light-dark cycle) or short (8:16-h light-dark cycle) days for 8 wk and then injected with either saline or 2-deoxy-D-glucose (2-DG), a glucose analog that inhibits cellular utilization of glucose and induces energetic stress. Long-day mice injected with 2-DG exhibited elevated corticosterone levels and reduced splenocyte proliferation compared with control mice. Short days buffered the animals against glucoprivation stress. Neither corticosterone levels nor splenocyte proliferation differed between 2-DG injected and control mice housed in short days. These data are consistent with the hypothesis that short days provide a buffer against metabolic stress.

Reduced aggressive behaviour in mice with targeted disruption of the oxytocin gene

Oxytocin (OT) has been reported to mediate aggressive and affiliative behaviours in several species. The behavioural role of OT has been established with physiological manipulations that potentially affected blood pressure, which may have indirectly affected the behaviours under study. To provide converging evidence of the physiological role of OT in aggressive behavior, wild type (WT), heterozygous (OT-/+), and homozygous (OT-/-) mutant mice were tested in two aggression paradigms. In general, there was no significant difference in aggressiveness between WT and OT-/+ mice. However, there were significant reductions in the duration of aggressive behaviors among OT-/- animals, especially in agonistic encounters within neutral arenas. The OT-/- mice did not exhibit any sensorimotor deficits or display any altered general anxiety levels that may have accounted for the observed reduction in aggressive behavior. These data indicate that aggression is mediated in part by OT in mice and that increased aggressiveness is not an obligatory phenotypic result of targeted genetic disruption of any gene.

The hypothalamic-pituitary-adrenal axis of prairie voles (Microtus ochrogaster): evidence for target tissue glucocorticoid resistance

Basal plasma corticosterone levels in prairie voles (Microtus ochrogaster) are extremely high, in the absence of any apparent negative consequences of glucocorticoid excess. We tested the hypothesis that prairie voles are a novel rodent model of target tissue resistance to glucocorticoids. Prairie voles had a significantly higher adrenal-to-body weight ratio, 5- to 10-fold greater basal plasma corticosterone, and 2- to 3-fold greater basal plasma ACTH concentrations than montane voles (Microtus montanus) and rats. While plasma corticosterone binding globulin (CBG) was 2-fold higher in prairie voles than in rats, both estimated and directly measured plasma free corticosterone were significantly higher in prairie voles than in rats. Plasma corticosterone levels in prairie voles were responsive to both circadian cues and a stressor, but were resistant to suppression by the synthetic glucocorticoid, dexamethasone (DEX). Western blots of brain and liver protein extracts, using a glucocorticoid receptor (GR) antibody, revealed the presence of a approximately 97 kDa immunoreactive band, the expected size for GR. Binding assays revealed significantly lower DEX affinity of corticosteroid receptors (CR) in cytosol of prairie vole brain and liver than that in the same tissues in rats. We conclude that prairie voles are a novel rodent model of glucocorticoid resistance, and that decreased affinity of CR for ligand might be partially responsible for this phenomenon.

Heteroaromatic analogs of 1-[2-(diphenylmethoxy)ethyl]- and 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazines (GBR 12935 and GBR 12909) as high-affinity dopamine reuptake inhibitors

A new series of heteroaromatic GBR 12935 [1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)-piperazine] (I) and GBR 12909 [1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine] (2) analogs was synthesized and evaluated as dopamine transporter (DAT) ligands. Analogs 5-16, in which the benzene ring in the phenylpropyl side chain of the GBR molecule had been replaced with a thiophene, furan, or pyridine ring, exhibited high affinity and selectivity for the DAT vs serotonin transporter (SERT) and stimulated locomotor activity in rats in a manner similar to the parent compound 2. In cocaine and food self-administration studies in rhesus monkeys, both thiophene-containing (6 and 8) and pyridine-containing (14 and 16) derivatives displayed potency comparable to 2 in decreasing the cocaine-maintained responding at the doses tested (0.8, 1.7, and 3 mg/kg). However, these compounds did not produce the degree of separation between food- and cocaine-maintained responding that was seen with 2. Among the bicyclic fused-ring congeners 17-38, the indole-containing analog of 2, 22, showed the greatest affinity for binding to the DAT, with IC50 = 0.7 nM, whereas the corresponding indole-containing derivative of 1, 21, displayed the highest selectivity (over 600-fold) at this site vs the SERT site.

Cellular immunity is not compromised by high serum corticosterone concentrations in prairie voles

Glucocorticoids compromise immune function in glucocorticoid-sensitive species (e.g., mice), but these immunosuppressive effects may be reduced in glucocorticoid-resistant species. Prairie voles (microtus ochrogaster) have been characterized as glucocorticoid-resistant to their high circulating levels of corticosterone. Because glucocorticoid-sensitive species display suppressed lymphocyte proliferation in response to elevated blood glucocorticoid levels, proliferative values were hypothesized to be reduced in house mice (Mus musculus) compared with prairie voles. Prairie voles exhibited significantly higher splenocyte proliferative responses to the T cell mitogen, Concanavalin A, despite having higher basal total and free serum corticosterone levels than mice. Neither total nor free serum corticosterone correlated with proliferative responses from either species. These data provide further evidence for glucocorticoid resistance in prairie voles and suggest that the interactions between the hypothalamic-pituitary-adrenal axis and the immune system in prairie voles may differ from those in mice or other glucocorticoid-sensitive species. Therefore, prairie voles may serve as a valuable animal model for the syndrome of glucocorticoid resistance in humans and the role of glucocorticoids in conditions characterized by a hyperactive immune system.

The effects of stress on social preferences are sexually dimorphic in prairie voles

Prairie voles (Microtus ochrogaster) are monogamous rodents that form pair bonds characterized by a preference for a familiar social partner. In male prairie voles, exposure to either the stress of swimming or exogenous injections of corticosterone facilitate the development of a social preference for a female with which the male was paired after injection or swimming. Conversely, adrenalectomy inhibits partner preference formation in males and the behavioral effects of adrenalectomy are reversed by corticosterone replacement. In female prairie voles, swim stress interferes with the development of social preferences and corticosterone treatments inhibit the formation of partner preferences, while adrenalectomized females form preferences more quickly than adrenally intact controls. Because sex differences in both behavior and physiology are typically reduced in monogamous species, we initially predicted that male and female prairie voles would exhibit similar behavioral responses to corticosterone. However, our findings suggest an unanticipated sexual dimorphism in the physiological processes modulating social preferences. This dimorphic involvement of stress hormones in pair bonding provides a proximate mechanism for regulating social organization, while permitting males and females to adapt their reproductive strategies in response to environmental challenges.

Adrenocorticoid hormones and the development and expression of mammalian monogamy

Based on research with prairie voles, we hypothesize that the unusual patterns of reproduction and social behavior associated with mammalian monogamy may arise as a consequence of normal developmental exposure to high levels of glucocorticoids and/or other hormones of the HPA axis. Increased HPA activity could functionally inhibit some of the masculinizing processes expected during the perinatal period. We hypothesize that the unique behavioral, physiological, and anatomical changes associated with monogamy may reflect the adaptive consequences of reduced exposure to the masculinizing actions of HPG hormones, such as testosterone. Reproductively naive, unpaired adult prairie voles also show unusual patterns of adrenal activity, including a marked decline in corticosterone levels within minutes following exposure to novel animals of the opposite sex. In females, this decline in corticosterone may contribute to pair bonding, since corticosterone injections inhibit, and adrenalectomy is associated with a facilitation of pair bond formation. In males, corticosterone injections facilitate pair bonding and adrenalectomy has the opposite effect. In animals from established social pairs corticosterone levels also fluctuate according to the social environment of the animal; the absence of a familiar partner is associated with increased corticosterone secretion, and in the presence of the familiar partner corticosterone levels tend to decline. Prairie voles may offer a valuable source of information regarding the behavioral, anatomical, and physiological consequences of long-term and short-term exposure to high levels of adrenal activity in the absence of pathology.

Modulation of pair bonding in female prairie voles (Microtus ochrogaster) by corticosterone

Glucocorticoid levels in animals may respond to and influence the development of social attachments. This hypothesis was tested in prairie voles (Microtus ochrogaster), monogamous rodents that form long-term heterosexual pair bonds. In socially naive female prairie voles, cohabitation with an unfamiliar male resulted in a dramatic decline in serum corticosterone levels. When corticosterone levels were reduced via adrenalectomy, females developed partner preferences after 1 h of cohabitation, while sham-operated and untreated females required 3 h or more of nonsexual cohabitation to establish a partner preference. In adrenalectomized and intact females, exogenous injections of corticosterone, given prior to social exposure, prevented the development of preferences for the cohabitating male. Although corticosterone inhibited the development of partner preferences, it did not interfere with the expression of previously established social preferences. These results suggest that social stimuli can modulate adrenal activity and that adrenal activity, in turn, is capable of influencing the formation of adult social preferences in female prairie voles. The involvement of the adrenal axis in the formation of partner preferences and the subsequent development of pair bonds provides a mechanism through which environmental and social factors may influence social organization in this species.

Physiological substrates of mammalian monogamy: the prairie vole model

Prairie voles (Microtus ochrogaster) are described here as a model system in which it is possible to examine, within the context of natural history, the proximate processes regulating the social and reproductive behaviors that characterize a monogamous social system. Neuropeptides, including oxytocin and vasopressin, and the adrenal glucocorticoid, corticosterone, have been implicated in the neural regulation of partner preferences, and in the male, vasopressin has been implicated in the induction of selective aggression toward strangers. We hypothesize here that interactions among oxytocin, vasopressin and glucocorticoids could provide substrates for dynamic changes in social and agonistic behaviors, including those required in the development and expression of monogamy. Results from research with voles suggest that the behaviors characteristics of monogamy, including social attachments and biparental care, may be modified by hormones during development and may be regulated by different mechanisms in males and females.